I know this is not what he asked but there is a great aspect of every gta
-GTA3 was the introduction of a 3D world and there are tons of mods for it
-Vice City had a nice feel, a greay storyline, and is easy to mod
-San Andreas had a big world, tons of new features, and lots of modding capabilities
-IV is like the change from GTA2 to GTA3. There are huge graphical improvements and many new features
Really I dont think any hardcore GTA player has a favorite because they all have their ups and downs